(L-r) IAN McSHANE as King Brahmwell, MINGUS JOHNSTON as Bald and EWAN McGREGOR as Elmont in New Line Cinemaâ€™s and Legendary Picturesâ€™ action adventure â€œJACK THE GIANT SLAYER,â€ a Warner Bros. Pictures release.

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(L-r) IAN McSHANE as King Brahmwell, MINGUS JOHNSTON as Bald and EWAN McGREGOR as Elmont in New Line Cinemaâ€™s and Legendary Picturesâ€™ action adventure â€œJACK THE GIANT SLAYER,â€ a Warner Bros. Pictures release.

(L-r) IAN McSHANE as King Brahmwell, MINGUS JOHNSTON as Bald and EWAN McGREGOR as Elmont in New Line Cinemaâ€™s and Legendary Picturesâ€™ action adventure â€œJACK THE GIANT SLAYER,â€ a Warner Bros. Pictures release.

+Read Caption

(L-r) IAN McSHANE as King Brahmwell, MINGUS JOHNSTON as Bald and EWAN McGREGOR as Elmont in New Line Cinemaâ€™s and Legendary Picturesâ€™ action adventure â€œJACK THE GIANT SLAYER,â€ a Warner Bros. Pictures release.

Hollywood’s been busy raiding the bin of public-domain fairy tales and spinning them around into edgier, though not necessarily improved, adaptations like “Red Riding Hood” and “Hansel & Gretel: Witch Hunters.” So it was only a matter of time until Jack and his towering beanstalk got the star treatment. But with “Jack the Giant Slayer,” it’s director Bryan Singer (“X-Men,” “X2”) who flouts his big-budget star power, putting spectacular special effects ahead of the story and its heroes.

Granted, the folk tale upon which the film is based isn’t exactly a gripping character study; a poor farm boy trades a cow for some magical beans, which sprout a massive stalk that takes him to a skyward land. There he steals from, and eventually kills, a man-eating giant. In Singer’s version, an orphaned Jack (Nicholas Hoult, “X-Men: First Class”) is working as a farmhand for an uncaring uncle who grows furious when the boy trades their only workhorse to a fugitive monk, desperate to unload the precious magical beans he just stole from the castle of King Brahmwell (Ian McShane), the benevolent ruler of 12th-century Cloister.

In fact, the beans were about to be employed by the king’s most trusted aide, Roderick (an unfortunately toothed Stanley Tucci), as the kickoff to his nefarious scheme to seize command of the giants, considered by most to be merely the stuff of legend, and conquer the kingdom. When the humble Jack inadvertently sprouts the stalk, the fair Princess Isabelle (Eleanor Tomlinson, “Alice in Wonderland”), visiting the farmhouse after becoming stranded in the rain, is vaunted toward the giants. The king dispatches a rescue crew that includes his highest-ranking royal knight (Ewan McGregor), Roderick and a seemingly outmatched Jack.

Despite the palace intrigue that sets it all in motion, the story itself is quite basic: rescue the princess, foil Roderick’s plot and don’t get killed by the monstrous giants who’ve been holding a grudge against humanity for eons. It’s all at the right level for a PG-13 audience, though older teens, and adults not accompanying kids, might find it all to be just a little too storybook.

The 3-D motion-capture giants, however, are most certainly going to catch and keep your attention (and potentially frighten younger kids, so mind the rating). Not only are they fast and ferocious, they are grotesque in appearance and manner. It’s hard not to lean back in disgust as they slobber, smear filth and chomp down on whatever sheep or human is unlucky enough to cross their path.

The giants are able to elicit such a strong reaction because of the in-your-face 3-D and motion-capture technology used to turn actors into these digital monstrosities. They’re also helped by the actors’ excellent voice work, particularly Bill Nighy as the vicious General Fallon and John Kassir as his lesser half — literally a shrunken, misshapen head that sprouts from Fallon’s neck and spews guttural, unintelligible exclamations of malicious support as they pursue the humans and squabble among themselves.

As revolting as the giants are, they are also the most interesting characters in the film, not exactly a winning formula for what is essentially a traditional hero’s journey.

Jack conquers challenges along the way to claiming his place in the world, but he does it rather quietly and without much flair, a fault of the script more than the actor. Although Princess Isabelle is introduced as a rebellious girl desperate to have her own adventure outside the castle grounds, she soon fades into a typical damsel in distress.

Even Ewan McGregor’s dashing knight turns bland, while Stanley Tucci’s power-hungry villain is too cartoonish to be considered much of a threat. Their costumes, however, imaginatively designed by Joanna Johnston, are a low-tech special effect that adds some visual interest on this most human of scales.

Alison Gang is the U-T’s movie critic. Email her at alison@alisongang.com